# Light As A Corpuscle

1. Jun 7, 2015

### Bashyboy

I am reading Schiff's book on Quantum Mechanics.He is discussing how Planck sought to account for the Blackbody radiation phenomenon, and correctly did so by assuming that the energy of light was described by the equation $E = h \nu$. He then claims that, because the energy of light is described by this equation, light is "sometimes like a stream of corpuscular quanta."

I am having difficulty seeing how $E = h \nu$ describing the energy of light implies that it is a particle. Couldn't light till be a wave and have its energy described by $E = h \nu$?

2. Jun 7, 2015

### Staff: Mentor

If the light is very intense then the energy delivered by the light per unit time is large; and if the light is dim then the energy delivered per unit time is small. However, the frequency and the wavelength of the light is the same in both cases, so the formula $E=h\nu$ yields the same constant value for $E$ in both cases.

Thus, Planck's hypothesis was that $E$ is the amount of energy delivered by a single corpuscle, and when a bright light is delivering a large amount of energy per unit time, that should be interpreted as a large number of corpuscles each with energy $E$ being delivered.

3. Jun 8, 2015

### harrylin

Somewhat yes. The point is that light is here described as consisting of a collection of entities with fixed energy. IMHO, "corpuscular" doesn't follow from that equation (what does follow from it is "quanta").

4. Jun 8, 2015

### sophiecentaur

The word "corpuscle" has fallen out of use because it doesn't imply the right properties for the packets of energy in which EM radiation is delivered (the photon). I blame dear old Richard Feinman for his insistence that the Photon 'is' a particle because it has caused so many beginners to hare off in an unhelpful direction in their studies. He understood what he meant but most people don't seem to. The particle he meant was not a 'little bullet' but people insist on viewing photons that way. It is not helped by the Feinman Diagram - which is purely symbolic - and which shows the photon as a wiggly line. drawn from place to place.